Disclosed are a copper alloy strip having high heat resistance and thermal dissipation properties which is suitable for a material for shield cans to solve heating of mobile devices, a material for vehicles and semiconductor lead frames, and a material for electrical and electronic parts, such as connectors, relays, switches, etc., widely used in industries including vehicles, and a method of preparing the same.

Disclosed is a high-strength free-cutting leadless copper alloy with excellent machinability and corrosion-resistance. The free-cutting leadless copper alloy contains 58 to 70 wt % of copper (Cu), 0.5 to 2.0 wt % of tin (Sn), 0.1 to 2.0 wt % of silicon (Si), a balance amount of zinc (Zn), and inevitable impurities but does not contain lead.

Disclosed is a high-strength free-cutting leadless copper alloy with excellent machinability and corrosion-resistance. The free-cutting leadless copper alloy contains 58 to 70 wt % of copper (Cu), 0.5 to 2.0 wt % of tin (Sn), 0.1 to 2.0 wt % of silicon (Si), a balance amount of zinc (Zn), and inevitable impurities but does not contain lead.

Bendability of a copper alloy wire is improved without decrease in an electrical conductivity of the copper alloy wire made of copper alloy containing zirconium. A cable includes: a two-core stranded wire formed by intertwining two electrical wires made of a conductor and an insulating layer covering the conductor; a filler formed around the two-core stranded wire; and a sheath formed around the filler and the electrical wire. The conductor is a copper alloy wire in which a precipitate containing the zirconium disperses, and has a crystal gain diameter that is equal to or smaller than 1 μm, an electrical conductivity that is equal to or higher than 87% IACS, and a tensile stress that is equal to or larger than 545 MPa.

Bendability of a copper alloy wire is improved without decrease in an electrical conductivity of the copper alloy wire made of copper alloy containing zirconium. A cable includes: a two-core stranded wire formed by intertwining two electrical wires made of a conductor and an insulating layer covering the conductor; a filler formed around the two-core stranded wire; and a sheath formed around the filler and the electrical wire. The conductor is a copper alloy wire in which a precipitate containing the zirconium disperses, and has a crystal gain diameter that is equal to or smaller than 1 μm, an electrical conductivity that is equal to or higher than 87% IACS, and a tensile stress that is equal to or larger than 545 MPa.

This pure copper plate or sheet contains 99.96% by mass or greater of Cu, in which when an average crystal grain size of crystal grains in a rolled surface is represented by X μm and an amount of Ag is represented by Y mass ppm, an expression of 1×10.sup.−8≤X.sup.−3Y.sup.−1≤1×10.sup.−5 is satisfied, and when a ratio of J3, in which all three grain boundaries constituting a grain boundary triple junction are special grain boundaries, to all grain boundary triple junctions is defined as NF.sub.JE and a ratio of J2, in which two grain boundaries constituting a grain boundary triple junction are special grain boundaries and one grain boundary constituting the grain boundary triple junction is a random grain boundary, to all grain boundary triple junctions is defined as NF.sub.J2, an expression of 0.30<(NF.sub.J2/(1−NF.sub.J3)).sup.0.5≤0.48 is satisfied.

This pure copper plate or sheet contains 99.96% by mass or greater of Cu, in which when an average crystal grain size of crystal grains in a rolled surface is represented by X μm and an amount of Ag is represented by Y mass ppm, an expression of 1×10.sup.−8≤X.sup.−3Y.sup.−1≤1×10.sup.−5 is satisfied, and when a ratio of J3, in which all three grain boundaries constituting a grain boundary triple junction are special grain boundaries, to all grain boundary triple junctions is defined as NF.sub.JE and a ratio of J2, in which two grain boundaries constituting a grain boundary triple junction are special grain boundaries and one grain boundary constituting the grain boundary triple junction is a random grain boundary, to all grain boundary triple junctions is defined as NF.sub.J2, an expression of 0.30<(NF.sub.J2/(1−NF.sub.J3)).sup.0.5≤0.48 is satisfied.

A copper alloy has a composition including 70 mass ppm or more and 400 mass ppm or less of Mg; 5 mass ppm or more and 20 mass ppm or less of Ag; less than 3.0 mass ppm of P; and a Cu balance containing inevitable impurities. In the copper alloy, the electrical conductivity is 90% IACS or more, and a length L.sub.LB of a low-angle grain boundary and a subgrain boundary and a length L.sub.HB of a high-angle grain boundary have a relationship of L.sub.LB/(L.sub.LB+L.sub.HB)>20%.

A copper alloy has a composition including 70 mass ppm or more and 400 mass ppm or less of Mg; 5 mass ppm or more and 20 mass ppm or less of Ag; less than 3.0 mass ppm of P; and a Cu balance containing inevitable impurities. In the copper alloy, the electrical conductivity is 90% IACS or more, and a length L.sub.LB of a low-angle grain boundary and a subgrain boundary and a length L.sub.HB of a high-angle grain boundary have a relationship of L.sub.LB/(L.sub.LB+L.sub.HB)>20%.

A copper alloy has a composition including: 70 mass ppm or more and 400 mass ppm or less of Mg; 5 mass ppm or more and 20 mass ppm or less of Ag; less than 3.0 mass ppm of P; and a Cu balance containing inevitable impurities. In the copper alloy, an average crystal grain size is in a range of 10 μm or more and 100 μm or less, an electrical conductivity is 90% IACS or more, and a residual stress rate is 50% or more at 150° C. after 1000 hours.